Accessing food resources: Rural and urban patterns of giving and getting food

Reciprocity and redistribution economies are often used by low-income households to increase access to food, adequate diets, and food security. A United States study of two high poverty rural counties and two low-income urban neighborhoods reveal poor urban households are more likely to access food through the redistribution economy than poor rural households. Reciprocal nonmarket food exchanges occur more frequently in low-income rural households studied compared to low-income urban ones. The rural low-income purposeful sample was significantly more likely to give food to family, friends, and neighbors and obtain food such as fish, meat, and garden produce from friends and family compared to the urban low-income group. Further, 58% of the low-income rural group had access to garden produce while only 23% of the low-income urban group reported access. In a rural random sample of the whole population in the two high poverty counties access to garden produce increased chances of attaining recommended vegetable and fruit servings controlling for income, education, and age. Access to a garden also significantly increased the variety of fruits and vegetables in diets.

不同降水量条件下C3植物红砂—C4植物珍珠混生光合特性研究

为探明种间关系和降水变化对混生植物群落光合特性的影响,以C₃植物红砂（Reaumuria soongarica）和C₄植物珍珠（Salsola passerina）为研究对象,沿自然降水梯度测定单生和混生红砂与珍珠光合参数。结果表明：混生可提高红砂的净光合速率、蒸腾速率、气孔导度,平均分别增加12.3%,13.7%,20.4%;而珍珠相反,平均分别减少5.5%,14.1%,28.9%。随降水的减少,混生红砂与珍珠的光合速率并没有显著提高,表明随干旱胁迫梯度增加其互惠作用并没有得到加强,并不支持胁迫梯度假说。西北干旱区和半干旱区红砂的净光合速率（Net Photosynthesis Rate,Pn）、蒸腾速率（Transpiration Rate,Tr）和气孔导度（Stomatal conductance,Gs）整体高于珍珠,平均分别增加6.6%,36.9%,27.8%,但其水分利用效率（Water Use Efficiency,WUE）低于珍珠,降低13.9%。研究表明,红砂可通过种间互惠更好地利用养分资源适应种间竞争及干旱胁迫环境,而混生珍珠竞争作用加强,在我国西北干旱和半干旱区红砂主要是通过提高光合速率来适应干旱环境,珍珠则通过提高水分利用效率来维持生长。     

白腐菌混合培养在胞外漆酶分泌上的种属互惠性

香菇、平菇、灵芝既是著名的食用菌 ,也是研究得相当广泛的白腐菌。香菇A3、平菇B2、灵芝KG菌株间两两混合培养 ,在胞外漆酶分泌状况上表现了较好的种属互惠性。研究结果显示 :A3 B2、B2 KG的混合培养体系表现了漆酶峰值提高、峰面积增大的优势 ,其中峰值情况为A3第 12d达 2 0 0单位 /g ,B2第 6d达 6 0 6单位 /g、KG第 10d达 5 76单位 /g ,A3 B2第 8d达 72 8单位 /g、B2 KG第 12d达 2 16 5单位 /g ;A3 KG的混合培养也在后、末期表现优于相应单株纯培养的漆酶状况。实验表明 ,不同种属白腐菌株混合培养对体系的漆酶分泌存在重要影响。